APPARATUS FOR INSTALLING A CABLE INTO A CONDUIT

Abstract

An apparatus including a blowing chamber house having a cable inlet opening, a cable outlet opening, a fluid inlet opening for receiving a supply of pressurized fluid. A fluid flow control for controlling flow of pressurized fluid to the fluid inlet opening of the blowing chamber house. A pushing drive and a conveyor including conveyer parts arranged at opposing sides of a cable guidance space and configured to be driven by the pushing drive. The control is arranged to determine a measure of resistance to a cable being installed into the conduit by the conveyor and for controlling the operation of the apparatus in accordance with the determined measure of resistance. The control is arranged to control the fluid flow control to increase the flow of pressurized fluid into the blowing chamber house in response to an increase in the determined resistance.

Claims

1. An apparatus for installing a cable into a conduit with the assistance of a fluid drag on the cable within the conduit, the apparatus comprising: a blowing chamber house having a cable inlet opening, a cable outlet opening, and a fluid inlet opening for receiving a supply of pressurized fluid, wherein the cable outlet opening is configured to be connected to the conduit and allow supplied pressurized fluid to flow into the conduit; a fluid flow control for controlling flow of pressurized fluid to the fluid inlet opening of the blowing chamber house; a pushing drive; a conveyor comprising: a first conveyer part; and a second conveyer part, wherein the first conveyer part and the second conveyer part are arranged at opposing sides of a cable guidance space and wherein one or both of the first conveyer part and the second conveyer part are configured to be driven by the pushing drive and thereby induce a driving force (Fdr) and a driving speed onto a part of the cable arranged in the cable guidance space; and a control is arranged to determine a measure of resistance to the cable being installed into the conduit by the conveyor and for controlling operation of the apparatus in accordance with the determined measure of resistance; wherein the control is means (17) are arranged to control the fluid flow control unit (14) in response to the said determined measure of resistance and/or to control the pushing drive unit (7) in response to the said determined measure of resistance; and wherein the control is means (17) are arranged to control the fluid flow control unit (14) to increase the flow of pressurized fluid into the blowing chamber house (10) in response to an increase in the said determined measure of resistance.

2. The apparatus according to claim 1, wherein the conveyor and the blowing chamber house are arranged to be mutually displaceable, and wherein the apparatus further comprises a force sensor arranged to measure a force between the blowing chamber house and the conveyor and provide a sensor output accordingly to the control, which is arranged to apply the sensor output to determine the said measure of resistance to the cable being installed into the conduit the conveyor.

3. The apparatus according to claim 2, wherein the blowing chamber house is displaceably arranged and the conveyor is fixed to a frame part of the apparatus, and the force sensor is positioned to measure the force between the blowing chamber house and the conveyor or a force between the blowing chamber house and the frame part of the apparatus.

4. The apparatus according to claim 1, further comprising a flow measurement sensor arranged to measure the flow of the pressurized fluid into the blowing chamber house and providing a flow measurement output accordingly to the control, and wherein the control is arranged to control the fluid flow control in response to the flow measurement output.

5. The apparatus according to claim 1, wherein the control is arranged to control the fluid flow control to increase the flow of pressurized fluid into the blowing chamber in case the determined measure of resistance exceeds a determined value.

6. The apparatus according to claim 1, wherein the control is arranged to control the pushing drive in response to the determined measure of resistance to reduce the driving speed induced onto the cable in response to an increase in the determined measurement of resistance.

7. The apparatus according to claim 6, wherein the control is arranged to reduce the driving speed induced onto the cable with 50% to 90% of a current driving speed of the cable in response to the determined measurement of resistance.

8. The apparatus according to claim 7, wherein the control is arranged to reduce the driving induced onto the cable when the said determined measurement of resistance exceeds a threshold value.

9. The apparatus according to claim 7, wherein the control is arranged to reduce the driving onto the cable when a rate of change of the determined measurement of resistance exceeds a threshold value.

10. The apparatus according to claim 1. wherein the control is arranged to control the pushing drive to terminate the driving of the cable by the conveyor in response to the determined measurement of resistance indicating an increase in the resistance to the cable being installed into the conduit by the conveyor.

11. The apparatus according to claim 1, wherein the control is arranged to control the pushing drive to reverse a driving direction of the cable by the conveyor in response to the determined measurement of resistance indicating an increase in the resistance to the cable being installed into the conduit by the conveyor.

12. An apparatus for installing a cable into a conduit, with the assistance of a fluid drag on the cable within the conduit, the apparatus comprising: a blowing chamber house having a cable inlet opening, a cable outlet opening, and a fluid inlet opening for receiving a supply of pressurized fluid, wherein the cable outlet opening is configured to be connected to the conduit and allow supplied pressurized fluid to flow into the conduit; a fluid flow control for controlling flow of pressurized fluid to the fluid inlet opening of the blowing chamber house; a pushing drive; a conveyor arrangement comprising: a first conveyer part; and a second conveyer part, wherein the first conveyer part and the second conveyer part are arranged at opposing sides of a cable guidance space and wherein one or both of the first conveyer part and the second conveyer part are configured to be driven by the pushing drive and thereby induce a driving force (Fdr) and a driving speed onto a part of the cable arranged in the cable guidance space; and a control for controlling operation of the apparatus, wherein the control is arranged to determine a measure of resistance to the cable being installed into the conduit by the conveyor; wherein the control is arranged to control the pushing drive to reduce the driving speed induced onto the cable with 50% to 90% of a current driving speed of the cable in response to the determined measure of resistance.

13. The apparatus according to claim 12, wherein the control is arranged to reduce the driving speed induced onto the cable when the determined measure of resistance exceeds a threshold value.

14. The apparatus according to claim 12, wherein the control is arranged to reduce the driving speed induced onto the cable when a rate of change of the determined measure of resistance exceeds a threshold value.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0057] An embodiment of the present invention is illustrated in the accompanying drawings of which

[0058] FIG. 1 is a side view of an apparatus according to the present invention,

[0059] FIG. 2 is a top view of the apparatus of FIG. 1, and

[0060] FIG. 3 is a sketch of the cable inside the conduit with indication of forces acting on the cable.

DETAILED DESCRIPTION

[0061] The figures show an apparatus 1 for installing an optical fibre cable 2 into a conduit 3. The apparatus 1 comprises a conveyor arrangement 4 comprising a first part 4a with a first chain 5a and a corresponding second part 4b having a second chain 5b, where the first chain 5a and the second chain 5b encloses a cable guidance space 6. A pushing drive unit 7 drives both chains 5a, 5b at a driving speed which is induced to the cable 2 placed in the cable guidance space 6 and provide a driving force Fdr on the cable 2. The clamping force Fc with which the first part 4a and the second part 4b of the conveyor arrangement 4 is clamping the cable 2 between the chains 5a, 5b is controlled by a clamping force arrangement 8. However, in other embodiments, the conveyor arrangement also provides a force to unwind the cable from a cable reel or cable drum, so that the driving force is a sum of the force needed to unwind the cable and the pushing force Fp.

[0062] The conveyor arrangement 4 is fixed to a frame part 9 of the apparatus 1. A blowing chamber house 10 is arranged displaceable, as indicated by the double arrow in FIG. 1, on the frame part 9 of the apparatus 1 and the conduit 3 into which the cable 2 is to be installed is connected to a cable outlet opening 11 of the blowing chamber house 10. The cable 2 is being guided from the conveyor arrangement 4 to a cable inlet opening 12 of the blowing chamber house 10 and from there to the cable outlet opening 11.

[0063] The blowing chamber house 10 is further equipped with a fluid inlet opening 13, which is connected to a source of pressurized fluid in the form of pressurized air (not shown) via a flow control valve 14. This is applied to create an airflow out through the conduit 3 to assist in carrying the cable 2 through the conduit 3 by inducing a drag force Fd on the cable 2. In alternative embodiments, other fluids such as water may be applied.

[0064] A force sensor 15 is provided between the conveyor arrangement 4 and the blowing chamber house 10 to provide a measure of the reaction force between the two, caused by the pushing force Fp on the cable 2 in the conduit 3 induced by the conveyor arrangement 4. In operation of the apparatus 1, the cable 2 in the conduit 3 is subject to the pushing force Fp from the conveyor arrangement 4, the drag force Fd from the fluid flow inside the conduit 3, and a friction force Ff from the friction between the inner wall 16 of the conduit 3 and the cable 2. The vector sum of these three forces Fp, Fd and Ff is substantially zero, as the cable 2 can be assumed not to accelerate substantially during operation of the apparatus 1. The magnitude of the pushing force Fp should be sufficient to overcome the difference between the drag force Fd acting in the same direction as the pushing force Fp, and the friction force Ff acting in a direction opposite of the two other forces Fp and Fd. In optimal operation of the apparatus 1, the direction of the pushing force Fp may actually be opposite to the drag force Fd, i.e. the conveyor arrangement 4 may slow the progress of the cable 2 into the conduit 3 as the magnitude of the drag force Fd from the fluid flow inside the conduit 3 exceeds the magnitude of the friction force Ff as the fluid flow will lift the cable 2 inside the conduit 3 and substantially avoid its contact with the inner wall 16 of the conduit 3. However, in less optimal operation of the apparatus 1, e.g. when the fluid flow rate is insufficient to lift the whole of the cable 2 from the inner wall 16 of the conduit 3 as illustrated in FIG. 3, the magnitude of the friction force Ff is larger and the direction of the pushing force Fp will be in the same direction as the drag force Fd.

[0065] The output from the force sensor 15 is considered to constitute a measure of the resistance to the cable 2 being installed into the conduit 3.

[0066] A flow measurement sensor 18 in the form of a Venturi tube sensor 18 is provided between the flow control valve 14 and the fluid inlet opening 13 of the blowing chamber house 10, which is arranged to measure the flow and provide a flow measurement output accordingly to the control means 17, which is arranged to control the flow control valve 14 accordingly.

[0067] The force sensor 15 provides an output to control means 17 of the apparatus, which is arranged to control the operation of the apparatus, including the flow control valve 14, which regulates the inflow of pressurized air into the blowing chamber house 10 and thus into the conduit 3 as well as the pushing drive unit 7 that determines the speed and/or pushing force Fp with which the conveyor arrangement 4 induces on the cable 2 situated in the guidance space 6. Furthermore, the control means may control the clamping force arrangement 8, which controls the force with which the first and the second part 4a, 4b of the conveyor arrangement 4 clamps the cable in the guidance space 6.

[0068] In operation of the apparatus 1, the control means 17 controls the pushing drive unit 7 to operate at a driving speed setpoint value with which the conveyor arrangement 4 drives the cable 2 into the cable inlet opening 12 of the blowing chamber house 10 from which the cable 2 moves out through the cable outlet opening 11 and into the conduit 3, which is fixed to the cable outlet opening 11. The blowing chamber house 10 is fixed to a frame part 9 of the apparatus 1 and is as such immobile at the operation of the apparatus 1. The control means 17 controls the flow control valve 14 to apply pressurized air to the blowing chamber house 10 via the fluid inlet opening 13, from which the flow of pressurized air is directed to the conduit 3. In the start-up of operating the apparatus 1 to install a cable 2 into the conduit 3, pressurized air at an initial flow rate setpoint is introduced into the conduit 3 when approximately the first 100 m of cable 2 has been installed into the conduit 3. As the cable 2 is driven further into the conduit 3, the friction force Ff between the cable 2 and the inner wall 16 of the conduit 3 will increase and so will the drag force Fd on the cable 2 from the fluid flowing in the conduit 3, both due to the longer length of the cable 2 being present inside the conduit 3. However, the friction force Ff will increase more than the drag force Fd, in particular in situations where the cable 2 undulates. This will result in an increase of the resistance to the cable 2 defined as the friction force Ff minus the drag force Fd, and the resistance will be counteracted by the pushing force Fp on the cable 2 from the conveyor arrangement 4 for keeping the speed of the cable 2 at the driving speed setpoint value.

[0069] As it is illustrated in FIG. 3, the cable 2 within the conduit 3 is subject to a pushing force Fp applied by the conveyor arrangement 4, a drag force Fd caused by the flow of pressurized air inside the conduit 3 and a friction force Ff from the contact between the inner wall 16 of the conduit 3 and the cable, which is moving at the driving speed from left to right in FIG. 3.

[0070] The force sensor 15 will detect the magnitude of the pushing force Fp and the control means 17 will, provided that the output received from the force sensor 15 exceeds a first predetermined level for more the 5 seconds, increase the flow rate setpoint with an amount determined by the cross-sectional area of the conduit 3 minus the cross-sectional area of the cable 2. The increase in flow rate will increase the drag force Fd on the cable 2 in the conduit 3 and lower the resistance to the cable 2, which will lower the pushing force Fp on the cable 2 and thereby the output from the force sensor 15 to the control means 17. This control cycle with increasing resistance measured by the force sensor 15 and the resulting increase of the flow rate setpoint will be repeated as the cable 2 is introduced further into the conduit 3 until the installation of the cable 2 is finalized or until the flow rate setpoint has reached a predefined maximum.

[0071] When the flow rate setpoint has reached the maximum value, the control means 17 will, in case the output from the force sensor 15 exceeds the first predetermined level for more than 5 seconds, control the pushing drive unit 7 to reduce the driving speed setpoint value by a predetermined amount, such as 5 meters per minute. By reducing the driving speed of the cable 2, the friction force Ff between the cable 2 and the inner wall 16 of the conduit 3 is reduced and the output from the force sensor 15 will drop below the first predetermined level. This control cycle may also be repeated as the cable 2 is introduced further into the conduit 3.

[0072] In case the cable 2 fails to advance inside the conduit 3 and instead curls up inside the conduit 3 as it is advanced into the conduit 3 by means of the conveyor arrangement 4, the friction force Ff between the cable 2 and the inner wall 16 of the conduit 3 and thus the output from the force sensor 15 will rise quickly and provide a warning sign for the control means 17. The control means 17 is adapted to determine the rate of change of the output from the force sensor 15, i.e. the change of the output over time, and if that rate of change exceeds a given threshold value, the control means 17 will control the pushing drive unit 7 to reduce the driving speed induced onto the cable 2 to a fraction of the current driving speed setpoint value, such as to 25% of the driving speed setpoint value. Thereby, the drag force Fd from the fluid flow inside the conduit 3 on the cable 2 present in the conduit 3 is allowed to straighten out the cable 2 and remove the curls of the cable 2 in the conduit 3 while the cable 2 is still advanced into the conduit 3 at a low driving speed. It has shown to be a more efficient method of resolving the problem of curling of the cable 2 within the conduit 3 than halting the advancement of the cable 2 completely, as the resumption of the feeding of the cable 2 into the conduit 3 with the current driving speed setpoint value will be more successful.

[0073] Alternatively to determine the rate of change of the output from the force sensor 15, the control means 17 may be adapted to detect that the output from the force sensor 15 exceeds a second predetermined level and reduce the driving speed induced on the cable 2 by the conveyor arrangement 4 to a fraction of the current driving speed setpoint value, such as 25% thereof.

[0074] In both cases, the control means 17 will determine when the output from the force sensor 15 drops below the first predetermined level for at least 5 seconds, where after the advancement of the cable 2 by means of the conveyor arrangement 4 at the current driving speed setpoint value is resumed.

[0075] Should the output from the force sensor 15 fail to drop below the first predetermined level after 60 seconds of the reduced driving speed of the cable 2, the control means 17 may control the pushing drive unit 7 to halt the driving of the cable 2 and reverse the driving direction of the conveyor arrangement 4 for e.g. 5 or 10 meters in order to straighten out curls of the cable 2 within the conduit 3, where after the advancement of the cable 2 by means of the conveyor arrangement 4 at the current driving speed setpoint value is resumed.

REFERENCE NUMBERS

[0076] 1 Apparatus

[0077] 2 Optical fibre cable

[0078] 3 Conduit

[0079] 4 Conveyor arrangement

[0080] 4a First part of conveyor arrangement

[0081] 4b Second part of conveyor arrangement

[0082] 5a First chain

[0083] 5b Second chain

[0084] 6 Guidance space

[0085] 7 Pushing drive unit

[0086] 8 Clamping force arrangement

[0087] 9 Frame part of the apparatus

[0088] 10 Blowing chamber house

[0089] 11 Cable outlet opening

[0090] 12 Cable inlet opening

[0091] 13 Fluid inlet opening

[0092] 14 Flow control valve

[0093] 15 Force sensor

[0094] 16 Inner wall of the conduit

[0095] 17 Control means

[0096] 18 Flow measurement sensor

[0097] Fdr Driving force

[0098] Fp Pushing force

[0099] Fc Clamping force

[0100] Fd Drag force

[0101] Ff Friction force

[0102] Aspects of the present invention are defined in the following items:

[0103] 1. Apparatus (1) for installing a cable (2), such as an optical fibre cable (2), into a conduit (3), with the assistance of a fluid drag, such as by means of a gas, on the cable (2) within the conduit (3), the apparatus comprising: [0104] a blowing chamber house (10) comprising a cable inlet opening (12) and a cable outlet opening (11) and a fluid inlet opening (13) for receiving a supply of pressurized fluid, wherein the cable outlet opening (11) is configured to be connected to the conduit (3) and allow supplied pressurized fluid to flow into the conduit (3), [0105] a fluid flow control unit (14) for controlling flow of pressurized fluid to the fluid inlet opening (13) of the blowing chamber house (10), [0106] a pushing drive unit (7), [0107] a conveyor arrangement (4) comprising a first conveyer part (4a) and a second conveyer part (4b), wherein said conveyer parts (4a, 4b) are arranged at opposing sides of a cable guidance space (6) and wherein one or both conveyer parts (4a, 4b) are configured to be driven by the pushing drive unit (7) of the apparatus and thereby induce a driving force (Fdr) and a driving speed onto a part of the cable (2) arranged in the cable guidance space (6), [0108] a force sensor (15) arranged to measure a force between the blowing chamber house (10) and the conveyor arrangement (4) and provide a sensor output accordingly, and [0109] control means (17) for controlling the operation of the apparatus in accordance with the sensor output provided by the force sensor (15),

[0110] wherein the conveyor arrangement (4) and the blowing chamber house (10) are arranged to be mutually displaceable.

[0111] 2. Apparatus according to item 1, wherein the blowing chamber house (10) is displaceably arranged and the conveyor arrangement (4) is fixed to a frame part (9) of the apparatus (1), and the force sensor (15) is positioned to measure the force between the blowing chamber house (10) and the conveyor arrangement (4) or the frame part (9) of the apparatus (1).

[0112] 3. Apparatus according to item 1 or 2, wherein the control means (17) are arranged to control the fluid flow control unit (14) in response to the sensor output provided by the force sensor (15) and/or to control the pushing drive unit (7) in response to the sensor output provided by the force sensor (15).

[0113] 4. Apparatus according to any of items 1 to 3, further comprising a flow measurement sensor (18) arranged to measure the flow of said pressurized fluid into the blowing chamber house (10) and providing a flow measurement output accordingly to the control means (17), and wherein the control means (17) are arranged to control the fluid flow control unit in (14) response to said flow measurement output.

[0114] 5. Apparatus according to item 3 or 4, wherein the control means (17) are arranged to control the fluid flow control unit (14) to increase the flow of pressurized fluid into the blowing chamber house (10) in response to an increase in the force between the blowing chamber house (10) and the conveyor arrangement (4) determined from the sensor output provided by the force sensor (15).

[0115] 6. Apparatus according to item 5, wherein the control means (17) are arranged to control the fluid flow control unit (14) to increase the flow of pressurized fluid into the blowing chamber house (10) in case the force between the blowing chamber house (10) and the conveyor arrangement (4) determined from the sensor output provided by the force sensor (15) exceeds a determined value.

[0116] 7. Apparatus according to any of the preceding items, wherein the control means (17) are arranged to control the pushing drive unit (6) in response to the sensor output provided by the force sensor (15) to reduce the driving speed induced onto the cable (2) in response to an increase in the force between the blowing chamber house (10) and the conveyor arrangement (4).

[0117] 8. Apparatus according to item 7, wherein the control means (17) are arranged to reduce the driving speed induced onto the cable (2) with 50% to 90%, such as with 65% to 80% of the driving speed, in response to the output from the force sensor (15).

[0118] 9. Apparatus according to item 8, wherein the control means (17) are arranged to make said reduction when the output from the force sensor (15) exceeds a threshold value.

[0119] 10. Apparatus according to item 8, wherein the control means (17) are arranged to make said reduction when a rate of change of the output from the force sensor (15) exceeds a threshold value.

[0120] 11. Apparatus according to any of the preceding items, wherein the control means (17) are arranged to control the pushing drive unit (7) to terminate the driving of the cable (2) by means of the conveyor arrangement (4) in response to the sensor output provided by the force sensor (15) indicating an increase in the force between the blowing chamber house (10) and the conveyor arrangement (4).

[0121] 12. Apparatus according to any of the preceding items, wherein the control means (17) are arranged to control the pushing drive unit (7) to reverse the driving speed of the cable (2) by means of the conveyor arrangement (4) in response to the sensor output provided by the force sensor (15) indicating an increase in the force between the blowing chamber house (10) and the conveyor arrangement (4).